This invention relates to the generation of electrical power from natural sources of energy, e.g., ocean waves, and particularly to the protection of the power generating system during conditions of excessively high levels of input energy, e.g., during ocean storms, while still operating the system for producing power.
One technique for protecting a power generating system during excessively high levels of input energy is simply to shut the system down; e.g., submerge a floating system normally responsive to the passage of ocean waves sufficiently deeply to be isolated from the surface storm conditions. A problem with this, however, is that power production is lost while the system is shut down.
Solutions are known where the power generating systems are only partially shut down; e.g., a system normally floating freely on the surface of an ocean is submerged beneath the surface but at a depth still responsive to the over-passing waves. Generally, however, such partial shut down solutions are complex and relatively slow operating.
The present invention provides a protection arrangement which is simple, inexpensive and quickly responsive to changing circumstances.
In a power generating system using an electrical generator for generating electrical output power from the system, protection against excessive input energy levels is obtained by increasing the current output from the generator to an amount greater than that would xe2x80x9cnormallyxe2x80x9d otherwise be generated at the generator output in response to the increased energy input. The higher than normal output current changes the system operating efficiency and increases the mechanical impedance of the system to a level higher than would be present if the xe2x80x9cnormalxe2x80x9d output current were being generated. The higher system mechanical impedance thus xe2x80x9cstiffensxe2x80x9d the system against the increased input energy, thus preventing for example, excessively high generator speeds of rotation. The system, while now operating at a less than optimum operating efficiency, continues to generate power.